Size-dependent aerosol activation at the high-alpine site Jungfraujoch (3580 m asl)

Henning, S.; Weingärtner, E.; Schmidt, S.; Wendisch, Manfred; Gäggeler, H. W.; Baltensperger, Urs

doi:10.1034/j.1600-0889.2002.00299.x

Cited by 71 publications

(68 citation statements)

References 36 publications

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“…Four dry particle threshold sizes (60, 80, 100 and 120 nm) were selected in order to cover different water vapour saturation ratios achieved inside clouds and to take into account the effect of aerosol chemical composition on the CCN activity (Dusek et al, 2006;Hudson, 2007;Quinn et al, 2008). Furthermore, the range of 60-120 nm represents reasonably well the minimum dry diameters of particles observed to act as cloud droplets (Henning et al, 2002;Komppula et al, 2005;Mertes et al, 2005).…”

Section: Data Analysis Methods Used On Measurement Datamentioning

confidence: 99%

Boundary layer nucleation as a source of new CCN in savannah environment

et al. 2013

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The South African savannah region is a complex environment of air pollution and natural emissions influenced by a strong seasonal cycle in biomass burning and strong precipitation. However, the scarcity of long-term observations means that the knowledge of controlling aerosol processes in this environment is limited. Here we use a recent dataset of 18 months of aerosol size distribution observations trying to understand the annual cycle of cloud condensation nuclei (CCN). Our observations show that the concentration of CCN-sized particles remains, in line with previous studies, high throughout the year with the highest concentrations during the dry winter and the lowest during the wet summer. During the wet season with reduced anthropogenic and biomass burning primary emissions, this pool of CCN is partly filled by boundary layer nucleation with subsequent growth. The enhanced importance of formation and growth during the wet season is addressed to increased biogenic activity together with enhanced free tropospheric removal decreasing the concentration of pre-existing CCN. During the dry season, while frequent new particle formation takes place, particle growth is reduced due to reduced condensing vapour concentrations. Thus in the dry season particles are not able to grow to sizes where they may act as CCN nearly as efficiently as during the wet season. The observations are compared to simulations by a global aerosol model GLOMAP. To our surprise, the global aerosol model utilized to explain the observations was not capable of re-producing the characteristics of particle formation and the annual CCN cycle, despite earlier good performance in predicting the particle concentrations in a number of diverse environments, including the South African savannah region. While the average yearly CCN concentrations of modelled CCN is close to observed concentrations, the characteristics of nucleation bursts and subsequent growth are not captured satisfactory by the model. Our sensitivity tests using different nucleation parameterizations and condensing organic vapour production rates show that neither of these is likely to explain the differences between observed and modelled nucleation and growth rates. A sensitivity study varying 28 modelling parameters indicates that the main uncertainties in the result are due to uncertainties in biomass burning emissions during the dry season, and anthropogenic sulphur emissions during the wet season, both in terms or emitted mass and particle sizes. The uncertainties appear to be mostly related to uncertainties in primary particle emissions, including the emissions variability not captured by monthly emission inventories. The results of this paper also highlights the fact that deficiencies in emissions estimates may result in deficiencies in particle production fluxes, while the end product such as modelled CCN concentration may be in line with observations

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Section: Data Analysis Methods Used On Measurement Datamentioning

confidence: 99%

Boundary layer nucleation as a source of new CCN in savannah environment

et al. 2013

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“…As suggested also by Henning et al (2002) we defined a period of CCN measurements as in cloud when the LWC was > 0.02 g m −3 for 85 % of the time and as out of cloud when the LWC was < 0.02 g m −3 for 85 % of the time. Figure 1.…”

Section: Liquid Water Content (Lwc)mentioning

confidence: 99%

Assessment of cloud supersaturation by size-resolved aerosol particle and cloud condensation nuclei (CCN) measurements

et al. 2014

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Abstract. In this study we show how size-resolved measurements of aerosol particles and cloud condensation nuclei (CCN) can be used to characterize the supersaturation of water vapor in a cloud. The method was developed and applied during the ACRIDICON-Zugspitze campaign (17 September to 4 October 2012) at the high-Alpine research station Schneefernerhaus (German Alps, 2650 m a.s.l.). Number size distributions of total and interstitial aerosol particles were measured with a scanning mobility particle sizer (SMPS), and size-resolved CCN efficiency spectra were recorded with a CCN counter system operated at different supersaturation levels.During the evolution of a cloud, aerosol particles are exposed to different supersaturation levels. We outline and compare different estimates for the lower and upper bounds (S low , S high ) and the average value (S avg ) of peak supersaturation encountered by the particles in the cloud. A major advantage of the derivation of S low and S avg from size-resolved CCN efficiency spectra is that it does not require the specific knowledge or assumptions about aerosol hygroscopicity that are needed to derive estimates of S low , S high , and S avg from aerosol size distribution data. For the investigated cloud event, we derived S low ≈ 0.07-0.25 %, S high ≈ 0.86-1.31 % and S avg ≈ 0.42-0.68 %.

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“…The CCNs are not, however, linearly connected to CDNCs, as the water depletion and other cloud processes can increase the actual cut-off diameter of cloud activation. In field experiments done at the top of mountains, a semi-direct measurement of the activated fraction to CDNC can be sometimes made, with activation diameters observed from 40 nm to over 200 nm (Henning et al, 2002;Sellegri et al, 2003;Lihavainen et al, 2008). Nevertheless, fixed activation diameters have been used as surrogates in several CCN-to-CDNC parameterizations (e.g.…”

Section: Relevant Metrics and Properties Of Sub-micron Size Distributmentioning

confidence: 99%

Number size distributions and seasonality of submicron particles in Europe 2008–2009

et al. 2011

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Abstract.Two years of harmonized aerosol number size distribution data from 24 European field monitoring sites have been analysed. The results give a comprehensive overview of the European near surface aerosol particle number concentrations Correspondence to: A. Asmi (ari.asmi@helsinki.fi) and number size distributions between 30 and 500 nm of dry particle diameter. Spatial and temporal distribution of aerosols in the particle sizes most important for climate applications are presented. We also analyse the annual, weekly and diurnal cycles of the aerosol number concentrations, provide log-normal fitting parameters for median number size distributions, and give guidance notes for data users. Emphasis is placed on the usability of results within the aerosol modelling community.Published by Copernicus Publications on behalf of the European Geosciences Union. We also show that the aerosol number concentrations of Aitken and accumulation mode particles (with 100 nm dry diameter as a cut-off between modes) are related, although there is significant variation in the ratios of the modal number concentrations. Different aerosol and station types are distinguished from this data and this methodology has potential for further categorization of stations aerosol number size distribution types.The European submicron aerosol was divided into characteristic types: Central European aerosol, characterized by single mode median size distributions, unimodal number concentration histograms and low variability in CCN-sized aerosol number concentrations; Nordic aerosol with low number concentrations, although showing pronounced seasonal variation of especially Aitken mode particles; Mountain sites (altitude over 1000 m a.s.l.) with a strong seasonal cycle in aerosol number concentrations, high variability, and very low median number concentrations. Southern and Western European regions had fewer stations, which decreases the regional coverage of these results. Aerosol number concentrations over the Britain and Ireland had very high variance and there are indications of mixed air masses from several source regions; the Mediterranean aerosol exhibit high seasonality, and a strong accumulation mode in the summer. The greatest concentrations were observed at the Ispra station in Northern Italy with high accumulation mode number concentrations in the winter. The aerosol number concentrations at the Arctic station Zeppelin in Ny-Ålesund in Svalbard have also a strong seasonal cycle, with greater concentrations of accumulation mode particles in winter, and dominating summer Aitken mode indicating more recently formed particles. Observed particles did not show any statistically significant regional work-week or weekday related variation in number concentrations studied.Analysis products are made for open-access to the research community, available in a freely accessible internet site. The results give to the modelling community a reliable, easy-touse and freely available comparison dataset of aerosol size distributions.

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Size-dependent aerosol activation at the high-alpine site Jungfraujoch (3580 m asl)

Cited by 71 publications

References 36 publications

Boundary layer nucleation as a source of new CCN in savannah environment

Boundary layer nucleation as a source of new CCN in savannah environment

Assessment of cloud supersaturation by size-resolved aerosol particle and cloud condensation nuclei (CCN) measurements

Number size distributions and seasonality of submicron particles in Europe 2008–2009

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